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TT Fitting

Old 01-30-12, 02:53 AM
  #1  
androidtt
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TT Fitting

So, I've preordered a tri-bike (SHIV Comp) and am pretty much set until the day it arrives. But I'm still questioning myself on the sizing which I can change up until the finalized date of 2/15. I'm not sure if this is strictly a triathlon thing, but I got a FIST fitting and according to it... My reach is 398 and my stack is 528. This puts me right around a Medium SHIV Comp (405/540; a difference of 7/12). The problem is that my standover height is 770ish in flat sandals and the Medium is 797. I demoed a Medium and needed to be standing on my cleats to stand over the bike.

So that led me to order a Small which is 385/515/772 (respectively). In that case I'm off 13/13 in the stack/reach department. Question: Which one of these numbers is more important? Do I sacrifice that extra 6mm/1mm difference for standover height? Will it even matter in a race situation? Is trending towards the smaller bike better anyways?

Thanks ahead of time. I got one good opinion on the question and was wondering if BF's racers could provide some input too.
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Old 01-30-12, 10:02 AM
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Hida Yanra
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For the new super-bikes, Tom D (founder of FIST fitting protocol) advocates getting the larger model, so that it can be run with as low in front as possible.
The low-in-front apparently more than cancels out the added size of the bike.

Now, not everyone would agree with that methodology, but that's probably what the FIST folks are going by.

If your bike is primarily for riding, and it works well for that, I'm unsure why you'd want a size that fits less well, just to improve your ability to throw a leg over it.
IMO, reach is a good bit more important as it is more likely to affect steering & balance on the bike. Lots of fast folks run their Shiv TT with a spacer stack, so there's less worrying on that end.
I'm assuming that you want to run all the equipment in the Shiv TT module (aerobars/stem/etc)... do you get multiple stem lengths & angles with the module?
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Old 01-30-12, 11:58 AM
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Stand over is the last thing I'd be concerned with. Seat tube length is first. If you have more than one size that will let you get the desired saddle/BB distance, then look at top tube length; specifically where you'll place the arm rests relative to saddle. This is the foundation of a comfortable, stable, and efficient position. Upper arms do best at around a 90 degree angle to the ground, and/or the arm rests depending on position of the extensions. The goal is to not have to use any muscle tension to sit on the bike.

I've done multiple fitting on tri and TT folks, quite a bit of the time I end up custom fabbing arm rests.

Rule of thumb is that they are mostly too far forward.

Confused on why a larger frame would provide a lower position given that head tube length goes taller as the frames go bigger.
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Old 01-30-12, 12:23 PM
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Originally Posted by Racer Ex View Post
Confused on why a larger frame would provide a lower position given that head tube length goes taller as the frames go bigger.
I think they mean that you want the largest size headtube for your fit, because the shaped headtube is more aero than round spacers.
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Old 01-30-12, 12:35 PM
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Originally Posted by Quel View Post
I think they mean that you want the largest size headtube for your fit, because the shaped headtube is more aero than round spacers.
Thanks.
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Old 01-30-12, 12:40 PM
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Originally Posted by Quel View Post
I think they mean that you want the largest size headtube for your fit, because the shaped headtube is more aero than round spacers.
Doesn't the Shiv have super aero spacers though? I remember seeing somewhere that it was fastest with the pads on the bar or with 2+ inches of spacers, but that could have been the Speed Concept.
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Old 01-30-12, 04:26 PM
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This seems on par with the advice I received earlier on ST from on of the members. Seems like the standover height isn't really an issue as I'll be on top of the bike 99% of the time. The thing is if I get the Medium, it's .7cm and 1.2cm bigger than my S&R numbers. So, I assume I'd have to stretch that extra bit? If I got the smaller one though I would need to adjust to a greater 1.3cm in both values. So that would mean making use of spacers... Contributing to less aerodynamics?

Oh, it's actually the SHIV-Tri version. Yes, it will come with a heap of spacers and the adjustibility of the front-end is suppose to be extremely accomodating. Still deciding on whether to get a higher version to have an integrated stem/handlebar + better components.
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Old 01-31-12, 06:58 AM
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Get the bike that you can fit to. If the medium will be too big, don't get it. No point in having the most aero bike on the block if your position sucks on it. I'd rather ride a small with a few spacers than the medium and be too high in front with no ability to go down. A spacer instead of headtube is probably some dumb difference like 2 seconds over 40k that aero weenies lust over, but the aero difference in position ins measured in minutes. Just looking at the numbers you are probably fine with the decision you made (small). But you paid good money to a fitter...go ask them in person!
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Old 01-31-12, 10:38 AM
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Originally Posted by Quel View Post
I think they mean that you want the largest size headtube for your fit, because the shaped headtube is more aero than round spacers.
Yep... horizontal stem, no spacers is best.
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Old 01-31-12, 11:51 AM
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Hida Yanra
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Originally Posted by Quel View Post
A spacer instead of headtube is probably some dumb difference like 2 seconds over 40k that aero weenies lust over, but the aero difference in position ins measured in minutes.
Originally Posted by Racer Ex View Post
...look at top tube length; specifically where you'll place the arm rests relative to saddle. This is the foundation of a comfortable, stable, and efficient position. Upper arms do best at around a 90 degree angle to the ground, and/or the arm rests depending on position of the extensions. The goal is to not have to use any muscle tension to sit on the bike.

I've done multiple fitting on tri and TT folks, quite a bit of the time I end up custom fabbing arm rests.

Rule of thumb is that they are mostly too far forward.
there you have it.
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Old 01-31-12, 06:45 PM
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Thanks thanks.
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Old 01-31-12, 10:53 PM
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Originally Posted by Hida Yanra View Post
For the new super-bikes, Tom D (founder of FIST fitting protocol) advocates getting the larger model, so that it can be run with as low in front as possible.
The low-in-front apparently more than cancels out the added size of the bike.

Now, not everyone would agree with that methodology, but that's probably what the FIST folks are going by.

If your bike is primarily for riding, and it works well for that, I'm unsure why you'd want a size that fits less well, just to improve your ability to throw a leg over it.
IMO, reach is a good bit more important as it is more likely to affect steering & balance on the bike. Lots of fast folks run their Shiv TT with a spacer stack, so there's less worrying on that end.
I'm assuming that you want to run all the equipment in the Shiv TT module (aerobars/stem/etc)... do you get multiple stem lengths & angles with the module?
he's talking about the 2012 shiv tri. the 2012 shiv TT is a different beast.
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